In terms of the earthen door question, I could 'theoretically' remove the bloom from the top but that is borderline impossible and then I would have no good way to clean the furnace. It honestly isn't too bad because I basically just shove a bunch of mud and rock in the hole until its good and insulated.
As for the bellows, I may try that once I get decent amounts of iron using the current setup. Once I get it down I can switch to the more challenging manual billows and see how much of a challenge that is!
RE: Smelting Iron Ore